A look at the historical precedents for Syria's most recent alleged chemical attack. It turns out that chemical warfare is thousands of years old.

Syrian opposition forces claim a nerve gas attack has killed hundreds, possibly thousands, of people just days after a team of UN chemical weapons inspectors arrived in the country to investigate earlier reports of chemical weapons use.

Photo and video footage uploaded to the Internet shows what appear to be lined-up dead bodies, including those of children, bearing no visible wounds. The footage also appears to show victims convulsing, foaming at the mouth, and displaying shrunken pupils—all possible signs of exposure to chemical agents. There has been no independent confirmation that the photos and video are accurate, and experts differ on what kinds chemicals they suspect were used.

The Syrian government is widely suspected of having stores of deadly sarin gas, but “you would expect to see first responders going down” from secondary exposure to sarin, Gwyn Winfield, editorial director of the global security journal CBRNe World, told The Guardian.

The French government is pressing for a forceful response if chemical weapons use is confirmed, and Israel says its intelligence supports witnesses’ claims that the recent attack was chemical—putting U.S. President Obama, who last August called chemical weapons a “red line” for intervention in Syria, in a difficult spot.

If a chemical weapon has indeed been employed in Syria, it wouldn't be the first time such an arsenal has been used. Below is a time line of major developments in the history of chemical and biological weapons:

circa A.D. 256 – Fire in the Hole

The oldest archaeological evidence of chemical warfare was found in Syria (though the area was controlled by Rome in the third century). According to University of Leicester archaeologist Simon James, burnt bitumen and sulfur—which create toxic compounds when added to fire—killed about 20 Roman soldiers, whose bodies were found piled in a tunnel in the city of Dara-Europos, still holding their weapons.

At the time, explains James, an army from the Sasanian Persian Empire was attacking the Roman-controlled city, digging tunnels underneath its walls. Roman forces also started tunneling in order to counter the invaders—but the Sasanians had chemistry on their side. "I think the Sasanians placed braziers and bellows in their gallery," says James, "and when the Romans broke through, added the chemicals and pumped choking clouds into the Roman tunnel."

1346 – A Plague on Their Houses

The Crimean city of Caffa, in what is now Ukraine, was under siege by a Tartar force when a mysterious plague overtook the invading fighters and swiftly cut down their numbers. At that point the ailing but resourceful Tartars decided to use their dead as artillery.

As notary Gabriel de' Mussi recorded several years later, the Tartars "ordered corpses to be placed in catapults and lobbed into the city in the hope that the intolerable stench would kill everyone inside."

The tack was all too effective. According to University of California, Davis professor Mark Wheelis, these catapulted corpses likely spread the Black Death to Caffa.

1763 – A Pox on the New World

During the French and Indian Wars, British General Jeffrey Amherst (namesake of the Massachusetts college) famously wondered in a letter, "Could it not be contrived to send smallpox among those disaffected tribes of Indians?" It's widely believed that the British attempted to use the disease as a weapon by giving smallpox patients' blankets to Native Americans.

Smallpox did devastate Native American populations around this time, though whether British blankets were responsible for an outbreak will likely never be proven. But centuries later, an outsize fear of weaponized smallpox remains.

1915 – Better Killing Through Chemistry

World War I became known as "the chemists' war," for the deadly gases it introduced to combat. At the Second Battle of Ypres, the German army released thousands of cylinders of yellow-green chlorine gas across the battlefield—the first major use of a chemical weapon in modern warfare. (Small amounts of tear gas had been used earlier by the French and Germans as an irritant.)

The gas, a choking agent that causes fluid to build up in victims' lungs, killed hundreds of French soldiers—at least; accounts vary—but didn't give the Germans an immediate advantage. It's been suggested that they themselves were so shocked by chlorine's effects that they failed to make an advance.

As gas attacks proliferated on both sides, soldiers learned to use cotton pads soaked in urine as a neutralizing mask. But mustard gas, another chemical agent used by both sides, was harder to escape and caused painful blisters to erupt on any exposed skin.

1925 – Enough Is Enough

In response to an estimated 100,000 casualties from gas attacks in World War I, the League of Nations drafted a document prohibiting chemical and biological warfare. The writers of the Geneva Protocol claimed that "the use in war of asphyxiating, poisonous or other gases, and of all analogous liquids, materials or devices, has been justly condemned by the general opinion of the civilized world." More than 30 nations signed the Geneva Protocol in 1925; today there are more than 100 signatories.

The United States, however, despite having pushed for a prohibition against chemical and biological weapons, did not sign until 1975—partially due to domestic opposition and worries that the protocol didn't go far enough.

1943 – A Catastrophic Scale

Napalm—a sticky, gasoline-like substance that can melt the skin off its victims—was developed in 1943 by Harvard chemist Louis Fieser and his team. Though it became infamous during the Vietnam War, napalm—which Fieser had found to be an effective weed killer—had a devastating impact during World War II, when a single U.S. firebomb raid in Tokyo killed an estimated 100,000 people. That's a comparable figure to the atomic bomb casualties at Hiroshima, and more deadly than the Nagasaki blast.

Yet a stranger napalm application never came to fruition: the napalm bat-bomb. Project X-Ray, as it was called, was a U.S. plan to release explosive bats—flying mammals strapped to napalm-laced time bombs—in Japanese cities, in hopes that the animals would find wooden houses to roost in and blow up. After several successful trial runs, the bat-bomb project was canceled when the officer in charge realized the arsenal wouldn't be ready for deployment until 1945.

1960s – Fatal to Flora and Fauna

Developed but not tested in the 1940s, the chemical weapon Agent Orange was meant to target plants, not people. During the Vietnam War, the U.S. Army sprayed local landscapes with this herbicide to destroy the opposition's food and cover—not realizing the health dangers it would pose to Vietnamese civilians and U.S. soldiers alike. Dioxin, the toxic ingredient in Agent Orange, can remain in the human body for over a decade, according to the Aspen Institute.

Half a century after the Vietnam War, those exposed to Agent Orange continue to suffer from its effects. In fact, the National Academy of Sciences has found potential links between Agent Orange and some cases of cancer, diabetes, and Parkinson's disease in U.S. veterans, as well as certain birth defects in children of veterans.

1980s – Agents of Doom

Nerve agents are the most lethal and quickest-acting category of chemical weapons. A single drop of sarin or the deadlier VX (the "V" in its code name indicates the "V-series," or venomous agents) can kill a person in minutes. Iraq became the first country to employ nerve agents on the battlefield when it released them as airborne chemicals, along with mustard gas, during the Iran-Iraq War. (Most nerve agents can also be administered in liquid form. They're tasteless in drinking water.)

Though a party to the Geneva Protocol, Iraq began employing chemical weapons against Iran as early as 1983. By 1988, reports had surfaced of nerve agents being used against Kurdish Iraqis in the north; one detailed the Iraqi government killing up to 5,000 Kurds in a single chemical attack at Halabja, possibly including deadly sarin and VX.

Today, these two nerve agents are among the chemical weapons in Syria's suspected arsenal.

1992 – A Premature Obituary

The World Health Organization declared smallpox eradicated in 1979. After that, only the U.S. and the U.S.S.R. were authorized to keep reserves of the variola virus, which causes smallpox.

Thirteen years later, Soviet defector Ken Alibek claimed the U.S.S.R. had been stockpiling variola for use as a biological weapon. It's unknown whether other countries were ever able to obtain variola samples from Soviet scientists, but Russia and the United States continue to hold onto hundreds of samples each, purportedly in case they ever need to develop a vaccine again.

Though the Russian government has never admitted to weaponizing smallpox, "we know that the Soviet Union's biological weapons program was doing experimentation with genetic modification," says Alan Zelicoff, director of Saint Louis University's Institute for Biosecurity.

Russia did eventually admit that a 1979 germ accident had actually been an outbreak of weaponized anthrax, a form of bacteria that is also a potent biological threat.

2001 – A Is for Anthrax, B Is for Bioterror

Shortly after the September 11 terrorist attacks, letters containing spores of the bacterium B. anthracis were mailed to media and public figures in the U.S. Five people died from contact with the anthrax—the country's first bioterrorism fatalities. In the following years, U.S. spending on biodefense rose exponentially, reaching more than $4 billion a year.

The anthrax attacks are generally believed to have been the work of one rogue government employee, Bruce Ivins. Ivins—who committed suicide in 2008 while under investigation for the attacks—was never charged.

Today, fear that biological and chemical weapons will fall into the hands of terrorist groups that are unconnected with state governments—and are unafraid to risk massive international devastation—still looms large.

'Though a party to the Geneva Protocol, Iraq began
employing chemical weapons against Iran as early as 1983. By 1988,
reports had surfaced of nerve agents being used against Kurdish Iraqis
in the north; one detailed the Iraqi government killing up to 5,000
Kurds in a single chemical attack at Halabja, possibly including deadly
sarin and VX. Today, these two nerve agents are among the chemical weapons in Syria's suspected arsenal."

......ATTN: Washington Post and New York Times, please note well and copy.

Also, re: ......those who so gleefully smirked that "No WMD's were found in Iraq" after Saddam's collapse.....Hmmm, wonder why?....does anyone of their editors remember those sightings of truck convoys crossing over into Syria during that approximate time?